EXHIBIT 99.1

                CERTIFICATION PURSUANT TO 18 U.S.C. SECTION 1350,
                             AS ADOPTED PURSUANT TO
                  SECTION 906 OF THE SARBANES-OXLEY ACT OF 2002

In connection with the Quarterly Report on Form 10-Q of PAREXEL International
Corporation (the "Company") for the period ended December 31, 2002 as filed with
the Securities and Exchange Commission on the date hereof (the "Report"), the
undersigned, Josef H. von Rickenbach, Chief Executive Officer of the Company,
hereby certifies, pursuant to 18 U.S.C. Section 1350, that:

         (1)      The Report fully complies with the requirements of Section
                  13(a) or 15(d) of the Securities Exchange Act of 1934; and

         (2)      The information contained in the Report fairly presents, in
                  all material respects, the financial condition and results of
                  operations of the Company.

Dated: February 14, 2003                       /s/ Josef H. von Rickenbach
                                               ---------------------------
                                               Josef H. von Rickenbach
                                               Chairman of the Board and Chief
                                               Executive Officer

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